Vehicle power supply system

ABSTRACT

A power supply and control system for a motor vehicle incorporating a plasma-assisted reactor for treatment of exhaust emissions and including a power source for supplying first and second output voltages.

This application is a 35 U.S.C. National Stage filing of PCT/GB00/00603filed Feb. 21, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to power supply systems and, morespecifically to a power supply system for use with an automotive vehicleincorporating a reactor for the plasma-assisted treatment of the exhaustgases from its associated engine to reduce the emissions of one or moreof nitrogenous oxides, particulate including carbonaceous particulate,hydrocarbons including polyaromatic hydrocarbons, carbon monoxide andother regulated or unregulated combustion products therefrom.

The principles of an arrangement for controlling corona dischargereactions in a corona discharge pollutant destruction apparatusemploying one or more corona discharge reactors in a motor vehicle aredescribed in U.S. Pat. No. 5,822,981. NOx, HC (hydrocarbon) and COremaining in exhaust emissions emerging from the corona dischargereactor are sensed and a computer uses data from these sensors and otherengine sensors to provide automatic control of power sources whichsupply the corona discharge reactors to adjust the power generationparameters to minimise the amount of pollutants in the treated gas. Thepower sources are, however, only shown indicatively in blockdiagrammatic form with no details of their components or how they aredriven.

Modern motor vehicles include more and more electrical equipment, someof which, such as electronic braking, electronic valve timing andelectrically operated power assisted steering systems consumeconsiderable amounts of power and require heavy cables if thetransmission power losses are to be kept to a reasonable level whenoperating with conventional 12 volt or 24 volt battery technology. Itshould be appreciated that in the automotive industry the principalbattery technology is the lead-acid battery system with a nominal 12volt output and open circuit voltage of 13.2 volts. The charging voltagerequired for a lead-acid battery is temperature-dependent but typicallyvaries between 13.6-13.8 volts that is a nominal 14 volts due to theopen circuit voltage of the battery. For the purposes of thisspecification we will use the industry adopted terminology of referringto battery voltages in multiples of the nominal 12 volts and toalternator outputs and charging voltages as multiples of the nominal 14volts. As battery technology develops differing open circuit andcharging voltages will apply and it will be it will be appreciated thatthe present invention is applicable to different battery voltages fromthose specifically referred to in the examples described in thisspecification. Power losses increase as the square of the electriccurrents flowing in the cables and vehicle manufacturers are consideringthe introduction of higher voltage standards such as 42 volts or 56volts for charging of 36 volts and 48 volt batteries. In the interimperiod due to the large number of 12/14 volt systems in service dualvoltage power systems are likely to be employed with two or morebatteries allowing lower power demand equipment operating at twelvevolts as at present and higher power demand equipment operating atthirty six, or even forty eight volts. This situation will beexacerbated when reactors for the plasma-assisted treatment of engineexhaust gases are fitted because such devices have a potential for highadditional electrical power demand under certain engine load conditions.

Power requirements can be illustrated by the example in which applying25 J per liter of exhaust gas flow to process the exhaust from a 250 kWtruck engine at full rated power would require approximately 6.25 kW.While this represents an acceptable 2.5% of rated power, it presents asignificant challenge as all of the power must be derived from thevehicle electrical power system. No single piece of electrical equipmenton a vehicle today represents a challenge of this magnitude.Transmission of 6.25 kW at 12 volts involves currents of 521 ampswhereas transmission at 36 volts requires 174 amps and at 48 volts, 130amps. However, at higher voltages such as 72 or 96 volts, currents arelowered significantly to 87 amp and 65 amp respectively. It is desirabletherefore to operate at the highest safe voltage when very high powerloading is anticipated. It is generally recognised that operatingvoltages less than or equal to 50 volts are considered safe andacceptable on vehicles and this is driving the standard of 42 volts or56 volts charging of 36 volt or 48 volt batteries discussed earlier. Itcan be seen however from the previous example that in some cases evenhigher voltages may be required to ensure efficient power transmissionto potentially high power demand systems such as plasma assistedemission control. In addition vehicle applications based on use of threeor even four output voltage sources in a vehicle are also of interest tomotor manufacturers.

Unlike other vehicle power demands it is not necessary to run anemissions after treatment systems when there are no emissions from thevehicle, that is, when the engine is switched off and therefore there isno need to be able to operate the system from the conventional vehicleelectrical supply incorporating the battery. An added benefit of thisapproach is that the absence of the battery in the circuit supplying theemissions control system enables less stringent regulation of voltage tobe employed. An economic benefit, that is, lower cost can arise fromthis feature.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a multiple-voltage powersupply system for use in automotive vehicles, in particular in a powergeneration and supply system which is capable of poweringplasma-assisted emissions control systems or other high power demandequipment, and in which, together with control functions, the problemsof safe and efficient operation are addressed.

According to the invention there is provided a power supply system for amotor vehicle incorporating a reactor for the plasma assisted treatmentof exhaust gases from an engine of the vehicle to remove noxiouscombustion products therefrom, a high voltage power supply adapted toproduce an output voltage sufficient to produce a plasma in exhaustgases from the engine of the vehicle as they pass through the saidreactor, an engine management system and a power management systemadapted to monitor operating parameters of the engine (such as enginespeed, throttle position, exhaust gas temperature, engine temperature),including the concentrations of the said noxious combustion products inthe exhaust gases, characterised in that there is provided incombination a plural-voltage generator adapted to produce a first outputvoltage suitable for the operation of lower power demand electricalequipment of the vehicle and a second output voltage which is higherthan the first output voltage, the said plural-voltage generator beingconnected to apply the second output voltage to the high voltage powersupply which generates therefrom the said output voltage sufficient toproduce a plasma in the exhaust gases, said engine and power managementsystems being adapted to monitor concentrations of noxious combustionproducts at both the inlet and outlet ports of the reactor, and to varya control variable of the high voltage power supply so as to adjust thepower supplied to the reactor to minimise the concentrations of the saidnoxious combustion products in the effluent from the reactor. In thisway the overall processing efficiency of the system is increased.

In some situations it will not be possible or desirable to installon-board emissions monitoring of exhaust gas components. In these casesthe existing engine sensors would be used to determine, viapre-programmed engine maps in the engine control unit, the levels ofemissions for a given engine load/speed combination. In addition it willnot always be possible or desirable to install a separate powermanagement system and in such cases the hardware and software would beincorporated into the engine management system.

Preferably the plural-voltage generator is adapted to produce a secondoutput voltage which is a multiple of the first output voltage.

Preferably the high voltage power supply includes an oscillatorcontrolled by the engine and power management systems to adjust thepower supplied to the reactor.

Preferably the high voltage power supply further includes a transformerto which the output of the oscillator is connected.

Preferably the first output voltage of the generator is a nominal 14volts, and preferably the higher voltage output is produced as analternating voltage the maximum values of which are symmetricallydisposed with respect to ground potential.

The generator may be an alternator and the higher voltage is produced bya winding which is centre-tapped to ground so as to reduce the peakvoltage by a factor of the square-root of three with respect to ground.For efficiency reasons it is preferable to run the voltage supplycircuit to the transformer at the highest acceptable safe levels as thisminimises power losses in cables and components. The booklet ‘Memorandumof Guidance on the Electricity at Work Regulations’ published by Health& Safety Executive, UK, 1990, page 21 suggests that safe operatingvoltages are 50 volts a.c. or 120 volts d.c. An additional benefit ofrunning at the highest acceptable voltages is that size and weight oftransformer are minimised as fewer windings are required due to the factthat the voltage step-up of the transformer is reduced.

In an alternative arrangement, the higher voltage output is produced asa d.c. voltage from one or more separate stator windings on thegenerator and in conjunction with a bridge rectifying circuit.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of a power supply system including areactor for treating exhaust gases from an internal combustion engine.For indicative purposes a nominal 12 volt battery circuit and a secondoutput voltage of 100 volts is shown.

FIG. 2 illustrates the high voltage power as including an oscillator anda transformer.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, there is shown a power supply system formobile applications such as a vehicle including a reactor 100 for theplasma assisted treatment of the exhaust gases from an internalcombustion engine 101 which powers the vehicle. The reactor 100 is forthe removal of noxious combustion products such as carbonaceousparticulates and/or nitrogenous oxides from the exhaust gases. Thereactor 100 may be a pellet bed reactor such as is described in ourpatent GB 2,274,412, a corona discharge reactor such as pulsed corona orcontinuous wave corona, a dielectric barrier reactor, a surface barrierreactor as described in our specification PCT/GB00/00079 or any othernon-thermal or thermal reactor for the plasma assisted treatment of theexhaust gases from internal combustion engines to remove noxiouscombustion products therefrom and may include catalytic components or beinstalled as part of an emissions control system employing catalysts orother emission control devices.

The reactor 100 is connected to a high voltage power supply, 102, whichin this example includes an oscillator and a transformer the oscillatorbeing connected to the high voltage output terminals of a dual-voltagealternator 103 which is driven by the engine 101 of the vehicle. Thereactor can be adjacent to its power supply as described in ourpublication WO99/05400 and the specification of our applicationPCT/GB00/00108. The alternator 103 is arranged to produce a first outputvoltage of for example fourteen volts or some other safe multiples forbattery charging and hence to operate the basic electrical equipment ofthe vehicle such as the lights, wipers, in-car entertainment and so on,together with a second higher output voltage, which may be a multiple ofthe first voltage and is likely to be 84 volts or 112 volts. In additionto being applied to the high voltage power supply 102, containing forexample an oscillator and a transformer the higher voltage output isavailable for use in operating other high power requirement equipmentwhich does not require connection to a battery circuit. The high voltageline also is connected to a load dump 104, as is a power managementsystem 105. The function of the load dump 104 is to absorb powertransients which w&ay occur as a result of the switching of high powerloads within the system.

In one embodiment a star wound alternator is used with the star pointconnected to the vehicle chassis. A full wave rectified output from thestar point to either one of the positive or negative outputs of thebridge rectifier provides the basic charging voltage for the vehiclebattery which can be for example 14 volts in current vehicles or 42volts or higher in future vehicles. Under this operational mode anadditional higher voltage output equal to the original voltage outputmultiplied by the square root of three (in this case 42 times the squareroot of three equals 71 volts) would be obtained between the positiveand negative terminals of the full-wave bridge rectifier. This highervoltage could be used as a more efficient power source for higher powerequipment. In a second embodiment where for example the equipmentpowered from the higher output voltage is more sensitive to ripple andtherefore a higher voltage regulation is required, a star delta 12-pulsefull-wave rectifier is used. This may have both star and delta statorwindings providing identical voltage outputs for example the chargingvoltage of the vehicle. This second embodiment can provide three voltageoutputs, the basic voltage, for example 42 volts between either polarityoutputs of the full-wave rectifier and the chassis earth point. Anoutput voltage of low ripple 84 volts between the two opposite polarityoutputs of the full-wave rectifier suitable for powering the high-powerdemand equipment and a third output voltage would be available from thestar point relative to the vehicle chassis, the latter voltage being thebasic voltage divided by the square root of three, thus a nominal 24volts from 42 volts. In a third embodiment the star and delta windingsmay be designed to give differing voltage outputs for example the starwinding may provide the 42 volt output for battery charging whereas thecombined output of the delta and star windings across the bridgerectifier can provide any other desired higher voltage. In thisembodiment the highest voltage output is no longer limited to 84 voltsand can be matched to the optimum voltage requirement for efficientoperation of the vehicle equipment.

Attached to the exhaust pipe 106 of the vehicle engine 101 at the inlet110 to and outlet 111 from the reactor 100, respectively, are sensors107, 108 and 109 which in this example are used to measure thetemperature of the exhaust gases from the engine 101, and theconcentration in the exhaust gases of those noxious combustion productsit is desired to remove from the exhaust gases. The exhaust temperaturedata are fed directly to the power management system 105. The noxiouscombustion products concentration data are fed to an emission controlmonitor 112 and thence to the power management system 105. The highvoltage power oscillator 102 also is connected to the power managementsystem 105 via a monitor/control link 113, as are an engine managementsystem 114, and a fuel supply system 115. Also connected to the powermanagement system are sensors 116 and 117, which measure the ambienttemperature and the engine drive conditions respectively.

In use the power management system 105 controls the output power levelfrom the high voltage power supply oscillator 102 from a minimum to amaximum as well as varying the duration of power pulses or other controlvariables, such as frequency or waveform in response to concentrationlevel signals from the emission control monitor 112 and signals from theexhaust gas temperature sensor 107 and the ambient temperature sensor116. The power management system 105 also monitors the operating stateof the engine 101 via the engine management and fuel supply systems 114and 115, respectively, so that the driving characteristics of the engineremain constant regardless of the demands made upon it by the powerdrawn by the reactor via the high voltage power supply unit 102 as itseeks to operate the reactor 100 so as to minimise the emission of thesaid noxious combustion products from the exhaust 106 from the engine101 of the vehicle.

In a second embodiment not shown the hardware and software functions ofthe power management system 105 are contained within the vehicle enginemanagement system 114 and all sensors and power connections originallyconnected to the power management system are connected directly to theengine control unit. In a third embodiment not shown the emissionscontrol sensors 108, 109 and the emissions control monitor 112 arereplaced by a pre-programmed engine map located within the enginemanagement and power management systems. In this configuration signalsfrom sensors such as 117 and 116 are used, together with thepre-programmed engine map, to determine the emissions level and hencethe optimum control variables for the plasma after treatment system.

In a fourth embodiment an integrated starter alternator damper system anexample of which is described in the article ‘Stop go systems get thegreen light’ in European Automotive Design, April 1998, pages 24-26 canbe used to power a plasma assisted emissions control system.

In a fifth embodiment, for efficiency reasons, the high voltage powersupply oscillator may be integral with the alternator 103. The powersupply is adapted to produce pulses having a potential of the order ofkilovolts to tens of kilovolts and repetition frequencies in the range50 to 5000 Hz, although higher frequencies of the order of tens ofkilohertz can be used. Pulsed direct current is convenient forautomotive use, but alternating potentials for example triangular orsine waves of the same or similar characteristics can be used.

What is claimed is:
 1. A power supply system for a motor vehicleincorporating a reactor for the plasma assisted treatment of exhaustgases from an engine of the vehicle to remove noxious combustionproducts therefrom, a high voltage power supply adapted to produce anoutput voltage sufficient to produce a plasma in exhaust gases from theengine of the vehicle as they pass through the said reactor, an enginemanagement system and a power management system adapted to monitoroperating parameters of the engine, including the concentrations of saidnoxious combustion products in the exhaust gases, wherein there isprovided in combination a plural-voltage generator adapted to produce afirst output voltage suitable for the operation of lower power demandelectrical equipment of the vehicle and a second output voltage which ishigher than the first output voltage and which is a multiple of thefirst output voltage, the said plural-voltage generator being connectedto apply the second output voltage to the high voltage power supplywhich generates therefrom said output voltage sufficient to produce aplasma in the exhaust gases wherein the high voltage power supplyincludes an oscillator adapted to be controlled by the engine and powermanagement system to adjust the power supplied to said reactor and atransformer to which the output of the oscillator is connected, saidengine and power management system being adapted to monitorconcentrations of noxious combustion products at both the inlet andoutlet ports of the reactor, and to vary a control variable of the highvoltage power supply for adjusting the power supplied to the reactor tominimize the concentrations of said noxious combustion products in theeffluent from the reactor.
 2. A power supply system according to claim1, wherein the first output voltage of the generator is a nominal 14volts.
 3. A power supply system according to claim 1, wherein saidsecond voltage output is produced as an alternating voltage the maximumvalues of which are symmetrically disposed with respect to groundpotential.
 4. A power supply system according to claim 3, wherein saidsecond voltage is produced by a winding which is center tapped to groundfor reducing the peak voltage by a factor of the square root of threewith respect to ground.
 5. A power supply system according to claim 1,wherein said second voltage output is produced as a d.c. voltage fromone or more separate stator windings on the generator and in conjunctionwith a bridge rectifying circuit.
 6. A power supply system according toclaim 1, wherein the oscillator is directly coupled to said secondvoltage output from the generator.
 7. A power supply system according toclaim 1, wherein said generator comprises an integrated starteralternator damper system.
 8. A power supply system according to claim 1,wherein said generator comprises an alternator driven by the engine andthere is no battery in the circuit of the higher voltage output from thealternator.
 9. A power supply system according to claim 8, wherein thereis a battery in the circuit of the first output voltage of thealternator.
 10. A power supply system according to claim 1, wherein saidgenerator comprises an alternator driven by the engine.